1. Field of the Invention
The present invention relates to a drive control apparatus and a drive control method for a matrix panel used with a display unit to display television image signals or computer output image signals, or with an electron source or the like that emits electrons.
2. Description of the Related Art
An image display apparatus using electron beams will be described as an example of a matrix panel implementing the present invention.
This type of image display apparatus conventionally has been known to have a multi-electron source for a matrix panel. The matrix panel includes a total of N×M cold cathode devices (image display devices) with N cold cathode devices arranged in the direction of rows and M cold cathode devices arranged in the direction of columns. These cold cathode devices are two-dimensionally arranged in a matrix pattern, and connected in a simple matrix wiring by M row wires (scanning wires) provided in the direction of rows and N column wires (modulation wires) provided in the direction of columns.
According to a typical method for driving a number of matrix-wired cold cathode devices, for each row of the matrix the devices in the row are simultaneously driven, with each of the devices of the each row being connected to a single row wire.
More specifically, a predetermined selection voltage selectively is applied to a single row wire, and a predetermined modulation voltage selectively is applied only to the column wire connected to the particular cold cathode device to be driven among the N cold cathode devices connected to that single row wire. Thus, a plurality of devices of one row simultaneously are driven by the potential difference between the potential of the row wire and the potential of the respective column wires. The row wires selectively are changed in sequence so as to scan all rows, thereby to form a two-dimensional image, making use of visual afterimages.
This method advantageously extends the drive time allocated to each device by N-fold, thus permitting higher brightness of an image display apparatus to be achieved, as compared with the method in which devices are scanned one-by-one.
This drive method presents a problem with respect to higher black level luminance. In other words, the black level is brighter, leading to a deteriorated contrast. As a solution to this problem, a method has been proposed in Japanese Unexamined Patent Application Publication No. 2002-221932, in which scanned wire drive time is controlled so as to lower the black level luminance, thereby to improve the contrast.
In the drive method described above, it is possible to control the scanned wire drive time in a predetermined horizontal scanning period by sequentially driving the scanned wires, thereby to reduce the black level luminance, which is an important factor in image quality. It is difficult, however, to improve display peak luminance, which is another important factor affecting image quality.